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<h1 style="direction:ltr;"><b><font color="#808000">AIMD with Decreasing Increases</b></font></h1>
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<h3>Notes:</h3>
<p style="direction:ltr;"><font color="#000000">This figure illustrates the difference between several AIMD algorithms used in some TCP variants and UDT.</font></p>
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<p style="direction:ltr;"><font color="#000000">The standard AIMD used in TCP is a straight line because alpha(x) is a constant value. In several high speed TCP variants, the data sending rate increases faster and faster, and the intuition is that a higher sending rate may indicate that the network bandwidth is higher so the sending rate should increase faster.</font></p>
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<p style="direction:ltr;"><font color="#000000">However, this scheme has two problems. The network bandwidth is fixed. As the sending rate becomes faster, the available bandwidth actually becomes smaller. A high increase parameter may cause large oscillations around the optimal bandwidth utilization. The second problem is related to fairness: if the flow with higher sending rate increases faster, the system may never converge to a fairness equilibrium.</font></p>
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<p style="direction:ltr;"><font color="#000000">This discussion leads us to use a totally different scheme. On the one hand, at the beginning when the data sending rate of a flow is slow, it should increase faster to approach the network bandwidth and catch up with those flows that have already a higher sending rate. On the other hand, when the data sending rate of a flow is high,  it should increase slower to avoid large oscillations.</font></p>
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